Per- and polyfluoroalkyl substances in tissues of intermediate egrets (Ardea intermedia) from the South China Sea

Despite decades of extensive production and applications of per- and polyfluoroalkyl substances (PFASs), their contamination in marine biota from the South China Sea (SCS) has received limited investigations. Aquatic birds are ideal biomonitoring indicators for environmental contaminants and associated ecological risks. In this study, we explored PFAS contamination in the tissues of intermediate egrets (Ardea intermedia), a representative aquatic bird with large population, inhabiting the islets of the SCS. Of the 17 PFASs analyzed, 11 were detected in tissues with detection frequencies ranging from 5 % to 100 %. The total PFAS concentrations (Σ₁₁PFASs) detected in the heart (0.25-9.01 ng/g ww) were significantly lower than those found in the liver (1.20-17.1 ng/g ww) and kidney (1.30-33.7 ng/g ww), likely due to tissue-specific protein levels and metabolic functions. Perfluorooctanesulfonic acid (PFOS), perfluorotridecanoic acid (PFTrDA), perfluoroundecanoic acid (PFUnDA), and perfluorononanoic acid (PFNA) were the predominant PFASs observed in bird tissues, although their composition varied slightly among different tissues. Moreover, the proportions of odd C-chain length PFCAs (i.e., PFNA, PFUnDA, and PFTrDA) were generally higher than adjacent even C-chain length PFCAs (i.e., PFDA, PFDoDA and PFTeDA). Overall, our study provides critical baseline data for further assessments of the potential ecological impacts of PFAS exposure in the island ecosystems of the SCS.